The present disclosure relates to joint prostheses, and particularly to prostheses having articulating head components. More specifically, the disclosure relates to a system for achieving variable positions for the head component of a joint prosthesis relative to a bone-engaging portion of the prosthesis.
Repair and replacement of human joints, such as the knee, shoulder, elbow and hip, has become a more and more frequent medical treatment. Longer life spans mean that the joints endure more wear and tear. More sports activities mean greater likelihood of serious joint injuries. Treatment of injuries, wear and disease in human joints has progressed from the use of orthotics to mask the problem, to fusion of the joint, to the use of prostheses to replace the damaged joint component(s).
As the success rate for total or partial joint replacements has increased, so too has the need for modularity and universality in the joint prosthesis. Patient variety means that no single size or configuration of joint prosthesis will suffice. The physical dimensions of a patient's joint components vary, as well as the bio-mechanic relationship between these components. For instance, in a shoulder prosthesis, the relationship between the articulating humeral and glenoid components can be significantly different between patients. These relationships are especially important where only one component of the joint is being replaced and must integrate with the existing natural opposing joint component.
For instance, in many shoulder surgeries, only the humeral component is replaced, leaving the glenoid component intact. In this case, it is imperative that the articulating surface of the humeral component match the articulating surface of the glenoid component as perfectly as possible, both statically and dynamically. With a typical humeral prosthesis, version and inclination are adjusted by the geometry of the head of the prosthesis. In other words, certain pre-determined head geometries are available that can be selected for a mating glenoid component. Absent an infinite variety of pre-determined head geometries, the resulting humeral prosthesis can often only achieve a best-fit relationship to the glenoid component of the shoulder joint.
In a typical surgical procedure, a trial component will be used to determine the optimum final component to be fixed to the bone. In most cases, the surgeon is able to make a good selection that fits the joint very well. However, in some cases, the accuracy of the fit cannot be determined until the surgery is completed and the patient has had an opportunity to exercise the repaired joint. Where significant problems arise, a revision surgery may be necessary to replace an improperly sized or configured joint component. One typical revision surgery requires removal of the entire prosthesis from the bone and replacement with a different prosthesis.
There is a significant need for a joint prosthesis that is both modular and universal. Such a prosthesis would be easily manipulated during the surgery and capable of achieving nearly infinite version and inclination angles. Moreover, an optimum prosthesis would be readily available for modification in a revision surgery without having to remove the entire prosthesis.
With the disclosed joint prosthesis a joint component is mounted to a bone engaging component of the prosthesis by an articulating mounting element. The articulating mounting element allows the joint component to adopt substantially infinitely variable ranges of angles in three dimensions relative to the bone engaging component.
In a one embodiment, the prosthesis is a humeral prosthesis for a shoulder replacement procedure. The humeral prosthesis includes a stem configured for engagement within the humerus. The stem defines a tapered bore facing the glenoid component of the shoulder joint. A distal portion of the mounting element is configured to be initially mobile within the bore, while a proximal end is configured to carry the humeral joint component or trial. The mounting element can be articulated to find the optimum position for the humeral joint component. The mounting element can then be temporarily tightened to hold the humeral joint component in position to verify the version and inclination angles of the component. The mounting element can be finally tightened to complete the humeral prosthesis.
The mounting element can be fixed in an orientation relative to the stem so as to fix the joint component in an orientation relative to the stem. Further, the mounting element and stem are configured to facilitate tightening the mounting element to the stem through achieving a friction fit with a tapered bore formed in the stem.
Several embodiments additionally utilize a second fixation mechanism. This second fixation mechanism includes a screw that is threaded into a threaded bore portion of the tapered bore in the stem. The screw bears against the mounting element to lock the element in position within the tapered bore.
The proximal portion of the mounting element defines a tapered surface that mates with a tapered feature of a head component for the humeral prosthesis. The head component can include an opening to access the passageway in the proximal portion of the mounting element, thereby providing access to the fixation screw in embodiments utilizing a fixation screw.
A number of joint components can be provided for interchangeable use to construct the prosthesis. For instance, a fixed mounting element can replace the articulating mounting element. Similarly, the head component for the joint prosthesis can be configured to mate directly with the stem, with the fixed mounting element or the articulating mounting element. The head component can also be modified to close the end of the passageway in the proximal portion of the articulating mounting element.
The joint prosthesis is advantageously both modular and adjustable. The joint prosthesis includes features that permit substantially infinitely variable positioning of a mating joint component relative to a bone engaging portion of the prosthesis.
The joint prosthesis is readily available for modification, whether during initial implantation or during a subsequent revision procedure. Preferably these features are combined in a joint prosthesis without creating a profile or prominence greater than is achieved by current joint prostheses.
In one embodiment, a method for mounting a joint component to a bone includes inserting a stem into the bone, positioning a solid articulating portion of a mounting element within a tapered bore associated with the stem so that the mounting element is substantially free to pivot in multiple degrees of freedom relative to the stem while maintaining substantially contiguous engagement between the solid articulating portion and a portion of a surface of the tapered bore defining a circle, engaging the joint component to a proximal portion of the mounting element, manipulating the mounting element to vary an angular position of the joint component relative to the stem with the mounting element positioned in the tapered bore while maintaining substantially contiguous engagement between the solid articulating portion and the portion of the surface of the tapered bore defining the circle, and mechanically locking the solid articulating portion in the tapered bore to fix a position of the mounting element relative to the stem after manipulating the mounting element by forcing the solid articulating portion toward a bottom of the tapered bore.
The above-noted features and advantages of the present invention, as well as additional features and advantages, will be readily apparent to those skilled in the art upon reference to the following detailed description and the accompanying drawings, which include a disclosure of the best mode of making and using the invention presently contemplated.
Corresponding reference characters indicate corresponding parts throughout the several views.